Not Applicable.
Automatic fastener drivers such as nail guns are well known. In a typical nail gun a pneumatic or otherwise powered driver actuated by a trigger mechanism drives nails from a coil of collated nails into a substrate.
When a sheet material or a layer of foam insulation is to be attached to the substrate, it is a common practice to employ a washer or cap with the nail or fastener. The washer or cap (which will be called a cap herein) has a larger diameter than the head of the fastener and is typically formed of a resilient material in a domed or concave shape, with the concave side of the cap facing toward the substrate. The outer edges of the cap resiliently grip the substrate material over a larger area than the fastener alone. When caps are used with fasteners, in the past it has been the practice to attach the fasteners by hand. Applicant has developed an automatic cap feeder that feeds a string of collated caps into alignment with a fastener driver so that the fastener is driven through the cap and carries the cap downwardly into contact with the substrate each time a fastener is driven. Applicant""s copending patent application, Ser. No. 09/380,871, filed Feb. 9, 1999, which corresponds substantially with applicant""s published PCT Application, International Publication No. WO99/39878, which is incorporated herein by reference, describes a preferred tool and cap feeder. Omli U.S. Pat. No. 5,947,362 also describes a cap feeder for a fastener driver.
In most applications, the cap is an injection-molded cap formed of a synthetic resin, such as high density polyethylene. When a nail is driven through a cap, the concave surface of the cap deflects resiliently to provide a resilient gripping outer edge that engages the substrate material. These caps have holes in the centers thereof for receiving nails. However, the holes are not essential, because the fasteners are metal and are able to pierce the caps even if they are not centered on the holes, which regularly occurs. It does not affect the functionality of the caps if the nails are somewhat off center.
When plastic caps are employed, as disclosed in the cited patent application, the plastic caps are held together edge to edge by a plastic tape that extends over the tops of the caps, with the caps then being wound on a reel with the concave sides of the caps facing inwardly.
The type of tape used to hold the caps together is important. A polyester tape coated with a silicone pressure sensitive adhesive, known as composite bonding tape, is preferred for plastic caps. This tape must have sufficient gripping power to stay attached to rather slippery plastic caps over a wide range of temperature variation. The tape also has to have a low level of elongation before it breaks and must be subject to tearing where a fastener penetrates the tape. The tape selected for the plastic caps is sufficiently strong that caps can be pushed along the slide track into a dispensing location without the tape breaking. However, when a nail or the like pierces the tape, the tape must easily tear and separate at that location. The caps are driven downwardly into the substrate via the nail when a nail is employed as the fastener, and the downward movement of the cap peels the tape off the cap and permits the tape to tear at the location where the nail has penetrated the tape. It is important that the tape be on the tops of the caps for this purpose so the tape will peel upwardly off the caps. Also when the tape is on the tops of the caps and the caps are coiled with the concave surfaces facing inwardly, more caps can be wound on a reel, and the caps are restrained from being peeled off the tape until they are dispensed.
Other possible ways for attaching caps together include molding the caps together in a strip, with a thin, breakable link extending between the caps; and molding the caps with a filament in the mold, by a process known as string collation. These processes are disclosed in more detail in applicant""s co-pending application.
In addition to plastic caps, it is desirable to be able to employ a metal cap with an automatic fastener driver. This presents substantial additional concerns, however. A metal cap has substantially different characteristics than a polyethylene cap, including resistance to fastener penetration and differing cling characteristics with adhesive tapes. If a metal cap is formed of a hard metal, for example, and the nail is not aligned with the hole in the cap, the nail may not penetrate the cap and it may cause the gun to jam and could damage the gun. Also, the tape must cling during normal temperature ranges and permit the caps to become separated when they are driven. The conventional tapes used for plastic caps are not ideal for metal caps.
An object of the present invention is to develop a collated cap assembly employing metal caps that can be employed in the same cap feeder apparatus as the plastic cap assemblies. Another object is to provide an improved cap feeder that more effectively feeds metal and plastic caps.
In accordance with the present invention, a cap assembly for an automatic cap feeder and fastener driver comprises a plurality of relatively thin metal discs that can be pierced by the fastener of a fastener driver such as a nail gun without damaging the nail or the gun, with the caps being connected together by a paper backed adhesive tape mounted on the undersides of the concave caps, with the caps having outer edges that cause the tape to be severed from the strip of caps when the caps are driven into a substrate after a nail has penetrated the caps.
In the preferred practice of the present invention, the caps are formed of a thin cold rolled steel having relatively sharp cutting peripheral edges with any burred edge facing up. Preferably, two sided galvanized steel is employed. The caps conventionally are approximately one inch in diameter and preferably are no greater than about 0.018 inches thick, desirably between 0.012 and 0.016 inches thick, and more preferably about 0.013 inches thick. The caps may have holes but do not require holes because the fasteners can be driven through the surface of the caps without a hole. Other metals such as aluminum or other steel can work as long as they can be pierced with the selected nail without bending the nail. The caps have a domed concave shape that enhances the peripheral gripping capabilities of the caps.
The preferred tape of the present invention is a paper backed tape coated on one side with a pressure sensitive rubber adhesive. Any substantial equivalent is satisfactory. This tape is similar in characteristics to masking tape. The preferred tape desirably is about xe2x85x9c inch wide and has a backing material 2 mils thick and an adhesive coating 3 mils thick. The tape dimensions can be varied, as long as the tensile strength of the tape is sufficient to permit the caps to be fed without tape breakage. Also the width of the tape is less than the width of the caps and the tape is positioned inside the edges of the caps, so that the caps will completely sever the tape when they are dispensed by a fastener driver.
An important feature of the tape is that it can be severed more easily under an impact load than a polyester tape (which tends to stretch more readily), and it is not necessary to first pierce the tape in order to create a weakened area where a stress tear will propagate. Polyester tape, particularly when applied to the tops of the caps, is undesirable because the sharp, upwardly facing burred edge on the metal caps tends to cut the tape.
With the caps of the present invention, the caps can be substituted easily for plastic caps in applicant""s automatic cap feeder and the caps themselves will sever the tape connecting the caps to the other caps as they are driven. The tape is then positioned under each cap and does not remain stuck to the outer surface of the cap, where it may be undesirable for aesthetic or functional purposes. Cap spacing is not too important with the use of paper backed tape positioned under the caps. A spacing of 0.050 of an inch is satisfactory.
The present invention also includes improvements in the cap feeding mechanism that facilitate feeding of metal and plastic caps with the same feeder. A new cover for a cap storage basket also is shown.
These and other features and advantages of the present invention are described in detail below and shown in the appended drawings.